Hume is often read as proposing an instrumental theory of decision, in which an agent's choices are rational if they maximally satisfy her desires, given her beliefs. In fact, Hume denies that rationality can be attributed to actions. I argue that this is not a gap needing to be filled. Hume's theory provides a coherent and self-contained understanding of action, compatible with current developments in experimental psychology and behavioural economics. On Hume's account, desires are primitive psychological motivations which do not have propositional content, and so are not subject to the criteria of rational consistency which apply to propositions.